1. Field
Embodiments of the present disclosure relate to method for fabricating bond pads. More particularly, embodiments of the present disclosure provide methods for controlling moisture in polymer material during bond pad fabrication.
2. Description of the Related Art
During chip packaging, metal layers are used for connecting solder material to bond pads that are electrically connected to semiconductor devices. An insulating layer is usually formed over the bond pad and patterned to expose portions of the bond pad. The metal layers, such as under bump metallization (UBM) or redistribution layers, are then formed over the patterned insulating layer and the exposed bond pads.
Bond pads are usually made with a conductive material, such as aluminum, copper, tin, nickel, gold, or silver. For aluminum bond pads, polymer materials are increasingly used as the patterned insulating layer for UBM or redistribution layer. However, polymer materials typically contain large quantity of moisture. The moisture can contaminate freshly cleaned aluminum surfaces. Moisture contamination degrades contact resistance between the aluminum bond pads and the UBM or redistribution layers.
FIG. 1 is a prior art schematic side view of an under bump metallization structure 100 subjecting to contamination caused by moistures in an adjacent polymer material. During packaging, a polymer layer 108 is deposited over a dielectric layer 102 and a device interconnect layer 104 of a fabricated device. The polymer layer 108 may be patterned to form a trench or via structure 106 exposing a bond pad area 104a. Under bump metal layers 110, 114 and 116 are then formed over the trench or via structure 106 and a solder material 118 is deposited thereafter to electrically connect the device interconnect layer 104. However, before depositing the under bump metal layer 110, moisture contained in the polymer material 108 usually contaminates the metal in the exposed bond pad area 104a forming undesired contaminations 112 between the device interconnect layer 104 and the under bump metal layer 110. The contaminations 112 reduce electrical conductivity between the device interconnect layer 104 and the under bump metal layer 110.
Traditionally, cooling the substrate or cooling the processing chamber is used to reduce moisture in the polymer. However, the cooling method is time consuming and not effectively.
Therefore, there is a need for methods for removing moisture from polymer materials positioned adjacent aluminum bond pads.